NGTS J214358.5-380102 - NGTS discovery of the most eccentric known eclipsing M-dwarf binary system
Jackman, James A. G.; Wheatley, Peter J.; Bayliss, Daniel; Moyano, Maximiliano; Eigmüller, Philipp; Casewell, Sarah L.; Gill, Samuel; Goad, Michael R.; Anderson, David R.; Burleigh, Matthew R.; Jenkins, James S.; Lendl, Monika; McCormac, James; Udry, Stéphane; Vines, Jose I.; West, Richard G.; Bryant, Edward M.; Watson, Christopher A.; Louden, Tom; Nielsen, Louise D.; Raynard, Liam; Acton, Jack S.; Tilbrook, Rosanna H.; Cooke, Benjamin F.; Belardi, Claudia; Alexander, Richard D.
United Kingdom, Germany, Chile, Switzerland, Austria
Abstract
We present the discovery of NGTS J214358.5-380102, an eccentric M-dwarf binary discovered by the Next-Generation Transit Survey (NGTS). The system period of 7.618 d is greater than many known eclipsing M-dwarf binary systems. Its orbital eccentricity of $0.323^{+0.0014}_{-0.0037}$ is large relative to the period and semimajor axis of the binary. Global modelling of photometry and radial velocities indicates stellar masses of MA = $0.426 ^{+0.0056}_{-0.0049}$ M⊙, MB = $0.455 ^{+0.0058}_{-0.0052}$ M⊙ and stellar radii RA = $0.461 ^{+0.038}_{-0.025}$ R⊙, RB = $0.411 ^{+0.027}_{-0.039}$ R⊙, respectively. Comparisons with stellar models for low-mass stars show that one star is consistent with model predictions whereas the other is substantially oversized. Spectral analysis of the system suggests a primary of spectral type M3V, consistent with both modelled masses and radii, and with spectral energy distribution fitting of NGTS photometry. As the most eccentric eclipsing M-dwarf binary known, NGTS J214358.5-380102 provides an interesting insight into the strength of tidal effects in the circularization of stellar orbits.